Getting back on thread. The idea of the crockoduck is facetious and ridiculous and shows that the author knows nothing about evolution, genetics or basically anything else.
I think there is more evidence accrued from multiple disciplines for our origins than there are for Relativity. Mind you, it is possible to genetically engineer a crockoduck I guess or something that could look like it. The problem is how it could survive without the intervention of people as we are its environment, should we create such an entity.
I postulate this as I think it could be done: the morality of such a venture is another issue. In the natural world crockoducks could not exist and should a mutant occur which looked somehow like a crockoduck as there is no way for them to survive or anyway to pass on their genes..which is very hard when you are dead. Such extreme mutants do not survive.